The present invention relates to the combination of a Savonius type rotor and a deflector plate device which serves as an augmentation apparatus that considerably increases the power output of the Savonius type rotor and also improves its self-starting ability and smoothness of operation. The invention also describes a novel Savonius type rotor of greater efficiency than existing Savonius type rotors. In connection with the rotor-deflector combination, the invention also features a simple, automatic speed control mechanism which can be efficiently used to facilitate stopping the rotor if desired.
As used in this application, the term "Savonius rotor" includes rotors having a shape as generally illustrated in this application and in U.S. Pat. No. 4,359,311, as well as rotors with two or more blades of the classic Savonius type, wherein the rotor blades are generally semi-cylindrical in shape. This is in contrast to turbines which have the inner edges of the blades fixed to adjoining blades or to a central core, drum or shaft in such a manner that there can be practically no crossing of the fluid past the inner edges of the blades.
High speed propeller type turbines have dominated the wind energy field largely because of their relatively high efficiency. Slow speed turbines such as the Savonius vertical axis turbine or the multi-blade horizontal axis windmill used for pumping water have typically been of low efficiency and cannot compete with the high speed propellor type for electrical power production. However, in addition to other disadvantages, there are some places where the high speed propellor type turbine cannot be installed. For example, they cannot be placed on floating platforms offshore because of possible damage to the propellor by the rocking motion of the platforms. They cannot be placed on top of large area flat buildings because the wind would be too unstable, and also the turbines would be too dangerous. With the high speed turbine, safety is an important consideration, and since metal fatigue is related to the number of stress reversed of high magnitude, it is difficult to predict when a blade may come loose from the turbine.
The applicant's U.S. Pat. No. 4,359,311 discloses a three blade vertical axis turbine offering substantial advantages over existing turbine devices.
As indicated in applicant's patent, existing Savonius type rotors have well known problems associated therewith. For example, they have low starting torque when oriented at certain directions and their action is jerky and pulsating under a load.
The present invention provides a novel, two blade Savonius type rotor of considerably improved efficiency, and somewhat better self-starting characteristics. In addition, the present invention provides a Savonius type rotor and deflector plate combination in accordance with the principles of the present invention which overcome the starting torque problem and gives a much smoother operation than existing Savonius rotors. The deflector plate augmentation device gives operating improvement to Savonius rotors in addition to considerably increased power output.